Cyclization Reactions of Aryl Propargyl Acetates with Tethered Epoxide Induced by Ruthenium Complex

Abstract

Reactions of the ruthenium complex [Ru]Cl ([Ru]=Cp(PPh ) Ru; Cp=η -C H ) with several aryl propargyl acetates, each with an ortho-substituted chain of various length containing an epoxide on the aromatic ring and with or without methyl substitutents on the epoxide ring, bring about novel cyclizations. The cyclization reactions of HC≡CCH(OAc)(C H )CH (RC H O) (R=H, 6 a; R=CH , 6 b, where RC H O is an epoxide ring) in MeOH give the vinylidene complexes 5 a-b, respectively, each with the Cβ integrated into a tetrahydro-5H-benzo[7]annulen-6-ol ring. A C-C bond formation takes place between the propargyl acetate and the less substituted carbon of the epoxide ring. Further cyclizations of 5 a-b induced by HBF give the corresponding vinylidene complexes 8 a-b each with a new 8-oxabicyclo-[3.2.1]octane ring by removal of a methanol molecule in high yield. For similar aryl propargyl acetates with a shorter epoxide chain, the cyclization gives a mixture of a vinylidene complex with a tetrahydronaphthalen-1-ol ring and a carbene complex with a tricyclic indeno-furan ring. For the cyclization of 18, with a longer epoxide chain, opening of the epoxide is required to afford the vicinal bromohydrin 22, then tandem cyclization occurs in one pot. Products are characterized by spectroscopic methods as well as by XRD analysis.

Green Synthesis of Dimethyl Carbonate from CO2 and Methanol: New Strategies and Industrial Perspective

“…When the electrode potential was ‐1.9 V at atmospheric pressure and 55 °C, 72% MeOH conversion at 100% DMC selectivity was achieved in the presence of [BMIM]BF 4 electrolyte and CH 3 I alkylating agent. [ 105 ]…”

“…The MeOH conversion can be significantly increased in the presence of CH 3 I or other costly additives. Liu and co‐workers [ 105 ] investigated the electrochemical synthesis of DMC in a three‐electrode cell reactor, equipped with a Pt foil as a counter electrode, Cu as a working electrode, and Ag/AgCl as a reference electrode. When the electrode potential was ‐1.9 V at atmospheric pressure and 55 °C, 72% MeOH conversion at 100% DMC selectivity was achieved in the presence of [BMIM]BF 4 electrolyte and CH 3 I alkylating agent.…”

“…When the electrode potential was -1.9 V at atmospheric pressure and 55 °C, 72% MeOH conversion at 100% DMC selectivity was achieved in the presence of [BMIM]BF 4 electrolyte and CH 3 I alkylating agent. [105] Lu and co-workers [106] developed a method for electrochemically synthesizing DMC. The transformation of MeOH to DMC could reach up to 73% at 100% selectivity to DMC in the presence of [BMIM]BF 4 saturated with CO 2 and CH 3 I as an alkylating agent at 55 °C using Cu as cathode material.…”

Intermolecular Dehydrative Coupling and Intramolecular Cyclization of Ruthenium Vinylidene Complexes Formed from Aromatic Propynes Containing Carbonyl Functionalities

“…Various transition metal vinylidene complexes are found to serve as important intermediates in these synthetically important organic transformations employing terminal alkynes –. The nucleophilic addition of Cβ of the vinylidene moiety onto a proper functional group is commonly observed, even though addition of the electrophilic Cα of the vinylidene moiety onto electron‐rich atoms is also possible . Recently, metal complexes of gold, palladium, copper, and tungsten have been shown to induce intramolecular cyclization of alkynes with oxygen‐containing functional groups, forming benzofuran rings .…”